leetcode: Symmetric Tree

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).

For example, this binary tree is symmetric:

1 / \ 2 2 / \ / \3 4 4 3

But the following is not:

1 / \ 2 2 \ \ 3 3

Note:Bonus points if you could solve it both recursively and iteratively.

题目描述：

对称树的判断。

代码实现：

/** * Definition for a binary tree node. * struct TreeNode { *int val; *TreeNode *left; *TreeNode *right; *TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:bool isSymmetric(TreeNode* root) {return root ? isSymmetric(root->left,root->right) : true;}bool isSymmetric(TreeNode *left,TreeNode *right){if(!left && !right) return true;//终止条件if(!left || !right) return false;//终止条件return left->val== right->val && isSymmetric(left->left,right->right) && isSymmetric(left->right,right->left);//三方合并}};

当你能飞的时候就不要放弃飞

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